1. Field of the Invention
The present invention relates to a crash detection apparatus of a vehicle for detecting a collision of a vehicle and for activating a passenger protective device for protecting its occupants.
2. Description of Related Art
FIG. 23, a schematic diagram showing a conventional crash detection apparatus of a vehicle disclosed, for example, in Japanese patent application laid-open No.3-208748/1991, illustrates a crash detection apparatus of a vehicle for activating a passenger protective device such as an air bag for protecting passengers (including the driver) in a vehicle. In FIG. 23, the reference numeral 1 designates a vehicle; 2 designates an air bag for protecting the passengers by deploying automatically in the event of collision of the vehicle 1; 3 designates an air bag ECU (Electric Control Unit) for controlling the deployment of the air bag 2 using an embedded acceleration sensor; and 4 designates a bumper switch that is mounted on a front bumper of the vehicle 1 and turns on in the event of collision of the vehicle 1.
Next, the operation of the conventional crash detection apparatus of the vehicle will be described.
In the event of collision of the vehicle 1 in traveling, the bumper switch 4 mounted on the front bumper of the vehicle 1 is turned on, and a collision signal is supplied from the bumper switch 4 to the air bag ECU 3. The air bag ECU 3, detecting the acceleration of the collision with the acceleration sensor installed in the air bag ECU 3, compares a predetermined threshold value with an integral value obtained by integrating over a fixed interval the acceleration signal supplied from the acceleration sensor during the collision, and deploys the air bag 2 under a decision that a crash takes place when the integral value exceeds the threshold value. The conventional crash detection apparatus of a vehicle controls the start of the deployment of the air bag 2 in response to the speed of the vehicle 1 at the time when the bumper switch 4 is turned on by the collision, thereby improving the decision performance of the crash.
With the foregoing arrangement, the conventional crash detection apparatus of the vehicle can detect the magnitude of the crash speed correctly within the same crash mode such as a frontal crash. However, besides the frontal crash, the vehicle 1 has other crash modes such as an offset crash, an oblique crash and a pole crash. Among these crash modes, the offset crash and the oblique crash generate an acceleration signal which is low immediately after a crash, but increases thereafter. Thus, the conventional crash detection apparatus of the vehicle, which simply integrates the acceleration signal over the fixed interval, or simply installs an auxiliary sensor such as the bumper switch 4 on the front bumper of the vehicle 1, has a problem of involving a delay in the crash decision.
The present invention is implemented to solve the foregoing problem. It is therefore an object of the present invention to provide a crash detection apparatus of a vehicle capable of making a more responsive crash decision even in an asymmetric crash mode such as an offset crash or a oblique crash which deforms only one side of a vehicle, and involves a delay in generating a large acceleration signal.
According to a first aspect of the present invention, there is provided a crash detection apparatus of a vehicle comprising: a plurality of collision detectors mounted on different positions of a vehicle for detecting a collision of the vehicle; and a crash mode identifying section for identifying a crash mode of the vehicle by comparing detection signals output from the plurality of collision detectors.
The plurality of collision detectors may each consist of an acceleration sensor for detecting an acceleration of the vehicle at a location at which the acceleration sensor is mounted; and the crash mode identifying section may identify the crash mode of the vehicle from a time difference between timings at which integral values obtained by integrating acceleration signals output from the acceleration sensors exceed a preset threshold value.
The plurality of collision detectors may each consist of an acceleration sensor for detecting an acceleration of the vehicle at a location at which the acceleration sensor is mounted; and the crash mode identifying section may identify the crash mode of the vehicle from a magnitude of a difference between integral values obtained by integrating acceleration signals output from the acceleration sensors.
The plurality of collision detectors may each consist of an acceleration sensor for detecting an acceleration of the vehicle at a location at which the acceleration sensor is mounted; and the crash mode identifying section may identify the crash mode of the vehicle from a time difference between peaks of integral values that are obtained by integrating acceleration signals output from the acceleration sensors.
The plurality of collision detectors may each consist of an acceleration sensor for detecting an acceleration of the vehicle at a location at which the acceleration sensor is mounted, and the crash detection apparatus of a vehicle may further comprise a plurality of filters each for filtering an acceleration signal output from the acceleration sensor.
The plurality of collision detectors may each consist of a mechanical sensor for generating a detection signal in response to an impact exceeding a predetermined level; and the crash mode identifying section may identify the crash mode of the vehicle from a time difference between timings at which the detection signals are output from the mechanical sensors.
The crash detection apparatus of a vehicle may further comprise a crash decision section for making a crash decision that a crash of the vehicle takes place, and the crash mode identifying section may determine a reference level for making the crash decision in accordance with the crash mode identified.
According to a second aspect of the present invention, there is provided a crash detection apparatus of a vehicle comprising: a collision detector mounted on a vehicle for detecting a collision of the vehicle; a first acceleration sensor mounted on the vehicle for detecting an acceleration of the vehicle; and a reference time acquisition section for obtaining from a signal fed from the collision detector a reference time for making a crash mode decision of the vehicle from an acceleration signal output from the first acceleration sensor.
Here, the collision detector may consist of a second acceleration sensor for detecting an acceleration at its mounted position; and the reference time acquisition section may determine, as the reference time for making a crash mode decision of the vehicle, a time at which an integral value obtained by integrating an acceleration signal detected by the second acceleration sensor exceeds a predetermined threshold.
The crash detection apparatus of a vehicle may further comprise a filter for filtering an acceleration signal output from the second acceleration sensor constituting the collision detector.
The collision detector may consist of a mechanical sensor for generating a detection signal in response to an impact exceeding a predetermined level; and the reference time acquisition section may determine, as the reference time for making a crash mode decision of the vehicle, a time at which the detection signal is output from the mechanical sensor.
The crash detection apparatus of a vehicle may further comprise a crash mode decision section for deciding a crash mode by comparing an integral value with a predetermined threshold value, the integral value being obtained by integrating over a predetermined period from the reference time the acceleration signal output from the first acceleration detector.
The collision detector may be mounted at a front of the vehicle, and the first acceleration sensor may be mounted behind the collision detector.